Biological considerations in the treatment of breast cancer: the "fall out" from clinical trials.

The evolution of the treatment for early breast cancer has now reached a critical period. At long last the conflicting claims of the anatomical and biological approaches towards treatment of this disease are being resolved by the application of prospective randomised clinical trials. The recognition that host factors exist which may place a constraint on the spread of cancer, and that haematogenous dissemination may occur long before the tumour has reached clinical proportions, has shaken the whole basis upon which "radical" cancer therapy is based. Furthermore, experimental work has suggested that lymphadenectomy or regional radiotherapy may produce sufficient disturbance to the immune competence of the host to allow the outgrowth of occult distant tumour foci. Prospective randomised clinical trials designed to determine the most effective local treatment have incidentally produced biological "fall out" which has thrown additional light on the behaviour and nature of breast cancer. It transpires that untreated mediastinal or axillary lymph nodes appear to have little growth potential of their own, or is it likely that they act as a reservoir for further metastatic dissemination. It is at last becoming accepted that irrespective of the extent of local therapy, the outcome for "early" breast cancer is predetermined by the extent of subclinical distant metastases at the time of presentation. In order to improve the results therefore, some form of adjuvant systemic therapy is essential. A number of clinical trials are at present underway designed to explore the most effective means of controlling minimal residual cancer following local ablation of the tumour.